mkDummySrc: also consider main.rs when deduping bins (#758)

checks/mkDummySrcTests/multibin/expected/Cargo.toml

@@ -5,6 +5,9 @@ path = "src/bin/hello.rs"
 [[bin]]
 name = "bye"
 
+[[bin]]
+name = "multibin"
+
 [features]
 default = ["some"]
 some = []

checks/mkDummySrcTests/multibin/expected/src/main.rs

@@ -0,0 +1,14 @@
+#![allow(clippy::all)]
+#![allow(dead_code)]
+#![cfg_attr(any(target_os = "none", target_os = "uefi"), no_std)]
+#![cfg_attr(any(target_os = "none", target_os = "uefi"), no_main)]
+
+#[allow(unused_extern_crates)]
+extern crate core;
+
+#[cfg_attr(any(target_os = "none", target_os = "uefi"), panic_handler)]
+fn panic(_info: &::core::panic::PanicInfo<'_>) -> ! {
+    loop {}
+}
+
+pub fn main() {}

checks/mkDummySrcTests/multibin/input/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "multibin"
+name = "multibin" # Loadbearing name matching bin
 version = "0.1.0"
 edition = "2021"
 
@@ -14,3 +14,6 @@ path = "src/bin/hello.rs"
 [[bin]]
 name = "bye"
 required-features = ["some"]
+
+[[bin]]
+name = "multibin" # Name of the package

lib/mkDummySrc.nix

@@ -199,6 +199,7 @@ let
         autobins = trimmedCargoToml.package.autobins or true;
         hasMainrs = autobins && hasFile srcDir "main.rs";
         srcBinDir = lib.optionalAttrs (autobins && hasDir srcDir "bin") (builtins.readDir (shallowJoinPath "src/bin"));
+        srcMainrs = "src/main.rs";
 
         candidatePathsForBin = name: rec {
           short = "src/bin/${name}";
@@ -231,9 +232,12 @@ let
               inherit (candidates) long;
               short = "${candidates.short}.rs";
             in
-            if lib.any (i: i == short || i == long) discoveredBins
-            then null
-            else short
+            if t.name == trimmedCargoToml.package.name
+            then (if hasMainrs then null else srcMainrs)
+            else
+              if lib.any (i: i == short || i == long) discoveredBins
+              then null
+              else short
         ));
 
         allBins = concatStringsSep " " (discoveredBins ++ declaredBins);
@@ -261,7 +265,7 @@ let
         cp ${writeTOML "Cargo.toml" trimmedCargoToml} $out/${cargoTomlDest}
       '' + optionalString (trimmedCargoToml ? package) ''
         # To build regular and dev dependencies (cargo build + cargo test)
-        ${lib.optionalString hasMainrs (cpDummy parentDir "src/main.rs")}
+        ${lib.optionalString hasMainrs (cpDummy parentDir srcMainrs)}
         ${stubBins}
 
         # Stub all other targets in case they have particular feature combinations